Page:Popular Science Monthly Volume 91.djvu/791

 Popular Science Monthly

��Applying a Change- Speed Device to an Automobile Clutch

INVENTORS have made many efforts to provide a change-speed mechanism for automobiles in order to dispense with the unsatisfactory gears now universally used. A system, to be effective, should be so arranged as to avoid intermesh'ing gears. For availability of control the ratio of speed should be indefinite, the speed increased or decreased by the simple movement of a wheel or lever, and devoid of friction while in operation.

The hydraulic system has been exploited in Various ways, but the devices, as here- tofore constructed, showed certain dis- advantages, namely: the liability of the expansion of the oil to such an extent as to injure the device or greatly lessen its efficiency; the in- ability to make the device small enough for easy installation ; the great weight in- volved ; the necessity for using both pumps and motors, and the slip due to leakage past the working parts.

The foregoing objections appear to be overcome by a new development of the hydraulic drive, which utilizes the clutch as one element in the change-speed mech- anism. The entire device occupies but a little more space than the male part of the standard clutch, which it displaces, as no clutch is necessary in using a car with this invention.

The drawings give a comprehensive view of the device, as all of the elements are shown in the two views. The body of the device is a cylindrical shell, the perimeter of which fits the standard clutch element inside of the fly-wheel. This is held in place either by friction or by means of cap- screws, so that it is permanently fixed to the wheel.

The rear side of the shell has a removable plate, the mechanism for changing the speed being secured to the inner surface of the plate, while the reversing mechanism is on the outside of the plate.

Within the shell are four radially- disposed cylinders, each cylinder having within it a piston, suitably packed with rings, following the usual practice. The

���The speed is changed by air pressure applied to the four cylinders used instead of the clutch

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stub-shaft, which enters the rear plate of the shell, has a single crank to which the four connecting rods are secured, so that the pistons have a successive motion to and fro as the shell turns, provided, of course, that the oil is confined in the pistons.

The head, or outer end of each cylinder, has ports on two opposite sides, the outer surface of each cylinder, along the ports, being planed flat and covered by slide valves which move axially, or parallel with the stub-shaft. The valves are re- shaped and provided with suitable openings to co-ordinate with the ports of the cylin- ders, each valve being designed to open or close the ports of two adjoining cylin- ders. To effect this, each L- valve has a stem which passes through the remov- able plate of the shell, the outer ends of these stems being rigidly attached to a rim which, although it turns with the shell, is, neverthe- less, easily adapted to connect with an operating lever.

It is obvious that, as the cylinders are rigidly attached to the shell, the stub-shaft will not turn if oil is permitted to freely pass in and out of the cylinders. The only effect in such a case would be to produce a reciprocating motion of the pistons. When, however, the driver of the car moves forward the lever which causes the L- valves to travel inwardly, and the ports of the cylinders are closed thereby, the pistons are restricted in their reciprocal motions, and the shaft turns, the rate of speed, relative to the engine speed, being dependent on the quantity of oil which is displaced at each revolution. If the ports are entirely closed, then the stub-shaft will travel at the same rate of speed as the engine-shaft.

It will thus be seen that there is no appreciable loss of power, and the slight amount of oil which escapes past the valves imparts a resiliency, or flexibility, to the car comparable to the electric or magnetic drive. There is not a single gear in the entire mechanism for driving the car forward.

For reversing, however, a train of gears is employed; or conical friction wheels may be used. A small bevel gear is fixed to the

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